Thermal printers have become popular during the last ten years or so and, broadly speaking, two types of thermal printers are now available. A first type of printer uses a thermally sensitive substrate on which to print, and a second type of printer uses a conventional substrate with a thermally sensitive ribbon interposed between a print head and the substrate. A machine in accordance with this invention may be used with either type of thermal printer but we prefer to use a printer of the second type which uses a thermally sensitive ribbon in combination with a conventional substrate.
It is an important feature of the invention that the machine is a flat bed printer so that the substrate is in a substantially flat position during the printing operation.
One advantage of flat bed printing as compared with printers in which a print head operates against a platen in the form of a roller is that a flat bed printer may more easily be used to print onto a relatively inflexible substrate which is difficult to bend around a platen in the form of a roller. On the other hand there is a problem with flat bed printing in that printing may be carried out over a relatively large flat area and in order to achieve a good printing result over the whole area it is important to make sure, as far as it is possible to do so, that the print head applies a predetermined required pressure to the substrate over the whole printing area while the substrate is sandwiched between the print head and the flat bed or platen of the printer.